Description: The Mountain Meadows Massacre, as it is known, occurred on Sept. 11, 1857, and was the first known act of religious terrorism on U.S. soil. A group of Mormons, many disguised as Paiute Indians slaughtered all but 17 small children on a wagon train of nearly 140 men, women and children traveling through Utah on its way to California. One man, the adopted son of Mormon leader Brigham Young, was eventually executed for the crime--20 years after the event. Hundreds of direct descendants of the massacre still assert that the iconic Brigham Young had complicity in the massacre, a view denied by the Mormon Church, even today.